Method and apparatus for studying laboratory animal behavior

Abstract

A walled enclosure or cage is provided in which laboratory animals may be maintained for observation and evaluation. The floor of the enclosure is provided by a plurality of conductive bar elements that are spacially separate and extend across the bottom of the enclosure. Spacial separation of the bars insulates one from the other and further, space is provided in the floor to remove animal waste, excess food and the like. An electrical resistor is connected between each two adjacent conductive bars and cooperate with the bars to define a resistor network to which a closely controlled feed current is supplied. An animal makes contact with the conductive bars which lowers resistance of the network and produces a voltage change. The resistor network is a.c. coupled to a differential amplifier, and a comparator which receive pulses from capacitors between the network and the amplifier and prepare same for an interface means for a pulse recording system. The amplified pulse may be shaped, divided or the like as required by the recording system. The method of using the present system involves detection of contact between an animal foot and the conductive grid bars, whereupon contact area determines the resistance of the network and a proportional signal is produced therefrom. The signal is then amplified, manipulated to avoid ambient electrical interference, such as an incidental electrical field from line current at 60 Hertz, and/or shaped, divided or the like to provide input to a particular recording system. Raw data from the recording system can then be correlated to locomotor activity of the laboratory animal.

What is claimed is: 
     
       1. Apparatus for measuring animal activity comprising: a. a walled enclosure;   b. a plurality of electrically conductive elongated elements received along a lower end of said enclosure and at least partially defining an animal floor thereat;   c. a plurality of resistors connected between said conductive floor elements and cooperating therewith to define a resistor network;   d. a current supply connectable to said resistor network, whereby an animal making contact with said conductive elements reduces electrical resistance of the network and causes a voltage change;   e. means to generate a pulse from said voltage change; and   f. means to manipulate said pulse and to segregate said pulse from ambient electrical interference, whereby said pulse provides input to a predetermined type of recording system.   
     
     
       2. Apparatus as defined in claim 1 wherein said walled enclosure is produced at least in part from transparent panels. 
     
     
       3. Apparatus as defined in claim 1 wherein said floor of said enclosure is defined by said conductive elements only. 
     
     
       4. Apparatus as defined in claim 1 wherein said conductive elements extend completely across said enclosure and are spaced apart from each other. 
     
     
       5. Apparatus as defined in claim 1 wherein said enclosure is comprised of a plurality of plastic panels secured to each other, two opposing panels having a plurality of matching openings along a lower edge thereof, and wherein said elongated electrically conductive elements are received in said matching openings and define said enclosure floor thereby. 
     
     
       6. Apparatus as defined in claim 1 wherein said current supply has means to control the current at an amperage below the tactile threshold of the animal. 
     
     
       7. Apparatus as defined in claim 6 wherein said means comprise a regulated voltage supply and current limiting resistors. 
     
     
       8. Apparatus as defined in claim 6 wherein said means comprise a regulated current supply. 
     
     
       9. Apparatus as defined in claim 1 wherein said pulse manipulating means comprise an amplifier and an interface means between the amplifier and a recording system. 
     
     
       10. Apparatus as defined in claim 9 wherein the interface means comprise a multivibrator to shape the pulse for the particular recording system. 
     
     
       11. Apparatus as defined in claim 1 wherein said manipulating means comprise an amplifier, a comparator, two multi-vibrators, a digital counter, and a relay and driver therefor, only certain of said manipulating means being actuatable at one time, whereby said system may be utilized with different recording systems. 
     
     
       12. An animal activity monitoring unit comprising: a. a walled animal enclosure, said enclosure having a plurality of elongated elements secured to a portion of said enclosure wall at opposite ends and defining a floor of said enclosure, at least certain of said elongated elements being electrically conductive;   b. resistors of predetermined value being connected across each adjacent electrically conductive element, and cooperating with said elements to define a resistor network, whereby upon receipt of a controlled current supply, a voltage change occurs when an animal makes contact with said conductive elements;   c. means to convert said voltage change to a pulse; and   d. means to manipulate said pulse to be compatible input for a particular pulse recording system, said means being connectable to said particular system.   
     
     
       13. Apparatus as defined in claim 12 wherein said enclosure walls are transparent to permit ready observation of an animal under study therein. 
     
     
       14. Apparatus as defined in claim 12 wherein all of said floor elements are conductive. 
     
     
       15. Apparatus as defined in claim 12 wherein said manipulating means comprises a plurality of different means, said different means being compatible with different recording systems, and switching means being included to actuate said different means as desired. 
     
     
       16. Apparatus as defined in claim 15 wherein said manipulating means comprise a differential amplifier, a voltage comparator, two multivibrators, a digital counter and a driver relay unit. 
     
     
       17. A method of monitoring animal activity comprising the steps of: a. placing a test animal in a walled enclosure, said enclosure having conductive grid bars defining a floor of same, said grid bars having resistors connected between adjacent elements and cooperating to define a resistor network;   b. providing a controlled current supply to said resistor network;   c. providing a stimulus for said animal;   d. permitting said stimulated animal to move about within the enclosure, each footstep on said electrically conductive element generating a voltage change in said resistor network;   e. converting said voltage change to a pulse; and   f. manipulating said pulse to be compatible with a particular pulse recording system.   
     
     
       18. The method as defined in claim 17 wherein said current is no more than 50 microamps. 
     
     
       19. The method as defined in claim 17 wherein said generated pulse is amplified by a factor of at least 1,000 is segregated from ambient electrical influence and is shaped for the particular recording system.